Spectroscopic observation of higher vibrational levels of C2 through visible band systems

Higher vibrational levels of the C2 molecule than those observed so far were investigated for the X(1)Σ(g)(+), A(1)Π(u), a(3)Π(u), c(3)Σ(u)(+), and d(3)Π(g) states through the Phillips, Swan, and d(3)Π(g)-c(3)Σ(u)(+) band systems under a jet-cooled condition. The term values and the molecular constants for 21 new vibronic levels were determined from rotationally resolved excitation spectra. The determined term values and rotational constants were compared to those derived from high-level ab initio potential curves. Perturbations identified in low J levels of the d(3)Π(g) (v = 8) state are most likely to be caused by the 1(5)Π(g) (v = 3) state.